Rewirable Cartridge Fuses

[andrex]

The 30amp (red) rewirable cartridge fuse on my consumer unit for the ring main is a larger size than the other smaller rated fuses. Provided there is enough spare capacity on the consumer unit could one of the smaller size fuse slots be used for a 30amp circuit.

[stevetravers]

no!

[Chippie]

Why do you want to up rate a smaller fuse?

The problem is not if the consumer unit has the capacity, Its the wiring. If you are 'blowing' fuses you must have a problem??

Give more details - I'll try and help.

Chippie

[Guest]

Hi,

I am not wanting to increase the size of an existing fuse - it's a new ring main circuit which I need to put into a spare slot in the consumer unit. The consumer unit has enough spare capacity but the only slot available will only take the physically smaller (not amps) rewirable fuse cartridge. The 30 amp fuse for the original ring main is a bigger type cartridge and fuse carrier. I have not been able to locate a supplier of replacement fuse catridges and carriers for this rather old MEM consumer unit.

Thanks

[Chippie]

Right, I see, seems to me your MEM consumer unit is rather outdated. I can only recommend you have it changed for a modern unit. This is not really a DIY job as the supply company should be involved in order to disconnect the incoming supply while the work is done. If you are not sure of what is involved please seek professional advice. Sorry I can't give you a simple way out.

Take care, Chippie

[andrex]

Thanks for helping. I am going to have a new consumer unit installed by the electricity company very soon.

Regards

[paulh53]

andrex wrote:

The 30amp (red) rewirable cartridge fuse on my consumer unit for the ring main is a larger size than the other smaller rated fuses

Not Heard Of "Rewirable Cartridge Fuses" Before

[oilman]

It's easy (with some) you suck the solder off the end caps, take out the old bits of wire, put a new piece of wire in and solder the ends up again. Only takes about 15 mins. Did one for Christmas tree lights, they kept blowing so removed the end caps from a fuse and soldered them onto a 180 ohm TR6 resistor, lights never blew again. (Yes, they did work)

[Millennium_Boy]

It is very dangrous, I'm surprised your house didn't burn down, as the lights were obviously faulty, and should have been thrown away (after cutting up to stop re-use), and a new set bought.

[BR]

I hope your joking, yes the lights will 'work' but in effect you are bypassing the fuse. If your Christmas lights keep blowing fuses there is a reason for it. For example they may be overloaded, shorting to earth or perhaps the fuse itself is overheating, due to the environments in which it is installed. Why put a resistor in place of the fuse?? What was the thinking behind using that over a piece of wire? If you are bypassing the fuse on a plug top this is one thing, removing a 30A ring main fuse is a lot more serious issue. I presume what this poster is referring to is a rewirable fuse holder (now out of date), in which the length of special fuse wire is run across the back of the holder, If the circuit is overloaded, this wire breaks and can then be replaced.

[oilman]

Right then, now you're all galloping across the quagmire without a thought for yourself let alone your horses, perhaps first, MB would like to demonstrate how my house is going to burn down by suitable calculations. (Remember I have done these, and the lights have been in use for over fifteen years, so how is it dangerous? hmm?) and by what logic do you draw your conclusions?

When you have stuck your head in the noose, I can give you a little more rope.

BR, perhaps YOU would like to explain what is the function of a fuse and how it accomplishes its function. Who said the lights kept blowing fuses? All mains fuses are miles too big for Christmas tree lights, but they DO have "fuse bulbs".

I agree totally that 30A mains fuses are very different but paulh53 did ask about "rewirable cartridge fuses". We know about rewirable fuses, and we know about cartridge fuses, and my reply was to this specific point. As for desoldering and replacing the wire in cartridge fuses, how do you think they were made in the first place?

[breezer]

putting a resistor in is like in your terms putting a pressure reducing valve in your main water supply and wondering why your shower doesn't work.

A fuse is basically there to protect what ever is connected to it, should something go wrong the fuse is designed to "self sacrifice" cutting off the electricity supply.

although some christmas lights do have a fuse lamp (most do now i admit) if it goes and there are no replacements available what are you going to do ? put in an ordainiry lamp? where is your protection now?

what if the cable to the lights gets trapped or say a metal tray falls edge on to the cable (not severing it but puncturing it) if you had a fuse it would self sacrifice a resistor may just get very hot (it may even explode!) which means in this case the tray you just dropped is now live, pick up tray and...............

No thanks, as an oil heating engineer would you put petrol in an oil boiler,(as fuel not in replacement of the water) its flamable isnt it? whats wrong with that it will burn get hot yeah marvelous good idea NOT!

( I AM USING PETROL AS A EXAMPLE OF WHAT NOT TO DO)

that is what you are doing by putting a resistor in place of a fuse.

You are a tradesman, would you use a toffee hammer to put in a 6 inch nail, course not, you would use the correct tool for the correct job

just out of interest fuse lamps are not as good as you may think, yes if it goes the lights will not work, but the live is still flowing all the way through the other lights, they dont work because the live stops at the fuse lamp, so if it for example at the end all the previos lights are still LIVE try it with a "volt stick" and see for your self

if the plug to fuse goes then all the lights will be dead since the fuse is in the plug before ANY of the lights

Normally i respect your posts and what you say, but resitor oilman, come on admit it you are practising for April the 1st

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[il78]

Funny........I remember you having a go at me for connecting a flexible hose to my oven saying it was "illegal" and not good practice. .......you leave the lights.....and I'll leave the flexie hose connected (which still is) also my house aint burnt down either

[oilman]

Hello breezer, you're not supposed to be giving hints to MB and BR.

I admit you are at a slight disadvantage here, as you wouldn't be aware of what I was doing for an undisclosed number of years before I started looking after oil boilers. I had done the calculations, and then carried out tests including those to establish what the worst case failure would be.

The domestic wiring fuse is more correctly there to protect the wire connecting to the thing, rather than the thing itself, you could pick a fuse with a specific characteristic to protect some things, but they would not normally be available for domestic wiring.

I'm afraid the comparison of petrol and a resistor is not particularly good, and as for oil vs petrol, one of the problems on some oil burners, is they do turn oil into something that is actually worse than petrol, as it has a higher energy density.

[breezer]

il78 wrote:

and I'll leave the flexie hose connected (which still is) also my house aint burnt down either

leaving the flexi hose in place is a "safety feature" if your house catches fire the hose melts letting out all the water putting out the fire

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